78 
layer is well preserved. This important fact has long been 
a desideratum in connection with English Palseo-phytology. 
This investing layer proves to be, as Professor Williamson 
in his previous memoir on Calamopitus had suggested was 
probably the case, a pareuchyma of somewhat remarkable 
structure, and of a thickness equal to that of the ligneous 
zone which it invests. But as the investigation of this new 
tissue is not yet completed, all further description of it must 
be reserved for some future occasion. 
“On the so-called Molecular Movements of Microscopic 
Particles,” by Professor Wm. Stanley Jevgns, M.A. 
Robert Brown, the celebrated botanist, first pointed out, 
in the year 1827, that minute particles of unorganized 
matter suspended in water exhibit movements which may 
easily be mistaken, and were formerly mistaken, for the 
movements of living animalcules. This motion is exhibited 
more or less by all substances which are reduced to a 
sufficiently fine state of division ( 5 oVo inch in linear mag- 
nitude to 50000), and the phenomenon is familiar to all 
occupied in microscopic observation. Vague suggestions 
have been often put forth that the motion is due to heat, 
to electricity, or to chemical affinity, but I have been able 
to find few published experiments on the subject, and 
those not of a conclusive kind. 
In investigating this phenomenon, I did not learn much 
by varying the solid suspended substance. The silicates, 
indeed, appeared to be generally the most active substances, 
and the purest quartz crystal when reduced to fine powder 
oscillated rapidly ; but such different substances as charcoal, 
red phosphorus, antimony, and sulphur were also very active. 
I cannot affirm that any substance is free from movement, 
but the metallic oxides, and the earthy salts such as car- 
